In the conventional bubble cap, sieve and valve trays the gas-or vapor-liquid contact (henceforth only spoken of as vapor-liquid contact) is achieved by bubbling the vapor through a layer of liquid that may have a depth of several inches. These deep liquid layers, created and maintained on top of the trays, are wholly structure-related, and are therefore independent of the vapor flow. As distinct from these arrangements the type of mass transfer trays with which the invention is concerned are of such a construction, and operate in such a way that there is film flow instead, and no important liquid depth at all. Moreover a significant portion of the kinetic energy of the vapor is used to create the liquid film, and move it over the expanse of the tray. In so doing the vapor is brought into effective contact with this nascent film, and effective mass transfer is thereby achieved between the vapor and liquid, without the vapor having to penetrate a deep liquid layer. The trays of this type are fitted with downwardly depending chimneys.
The mechanism promoted by such trays has been presented in more detail in an initial publication of the inventor in the Trans, Inst. Chem. Engineers, Vol. 40, No. 2, pages 104-113, 1962. Other descriptions of such mass transfer trays are also given in U.S. Pat. Nos. 3,075,752 and 3,367,638, where various designs are discussed, with some emphasis on the choice of the shape of the depending chimneys. As will be noted the chimneys described in those specifications do in all instances represent distinctly separate entities, fitted and attached by various means to the horizontal tray deck itself.